L9965TS datasheet(2/62 Pages) STMICROELECTRONICS

2 / 62 page

Overview

In a high voltage battery management system, the master microcontroller accesses the cells monitor and the pack

current monitor devices for diagnostics and control purposes. Since the different BMS ICs are located into

different voltage domains, it is required isolated communication between each other.

The L9965T/TS allows isolated daisy chain connection through a simple two-wire protocol in L9965x-based HV

BMS applications. It converts data from a standard 4-wire SPI protocol to a 2-wire proprietary protocol (and vice

versa), supporting the signals isolation by capacitors or transformers.

All the devices in the daisy chain recognize the protocol and can be addressed in read-write mode by a single

transceiver. Ring connection can be implemented by the dual channel device L9965T.

L9965T/L9965TS implements two physical communication interfaces.

•

SPI Target Interface: this interface is used by the controller MCU to configure and send commands to

L9965T/TS and, through it, to all the devices in the chain.

•

Isolated Vertical Interface (VIF): this interface is typically used to connect BMS daisy-chained devices

L9965A/C to L9965T/TS and to each other on the VIF bus.

Figure 1. L9965T in a L9965x-based BMS system

BJB

BMU

CMC

V, T sense

Balance

HV+

HV-

SBC/PMIC

MCU

L9965A

CAP or

transformer

CAP or

transformer

COMH

Optional ring

connection

COML

V, T sense

Balance

L9965A

CAP or

transformer

COMH

COML

CAP or

transformer

SPI

Transformer

L9965T/TS

L9965P

Transformer

CAP or

transformer

L9965C

COMH

COML

CAP or

transformer

The L9965T/TS manages periodic wakeup of the devices in the chain for diagnostic purposes and it is sensitive to

fault tones from the devices in the chain when in low power mode. It implements a set of commands to optimize

the communication over the chain:

•

Broadcast command, to write and configure all devices in the chain (or a subset)

•

Burst and compressed burst read, to enable high data rate transmission from all devices in the chain with

negligible impact on the power consumption

•

Go-to-sleep command, to set all the devices in the chain to low power mode

•

FAULT/WAKEUP tone, to wake-up the chain for normal operation or faults signaling

•

CYCLIC_WAKEUP tone, to trigger periodic diagnostic execution in the chained devices.

These functionalities are implemented using different functional states, to optimize system power consumption:

•

NORMAL: full operation mode

L9965T/L9965TS

Overview

DS14987 - Rev 1

page 2/62

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